It is known in the art to deposit a diffuser coating onto a surface of a substrate where the coating is atomized via pressurized air at an exit port of a liquid material or solution. The pressurized air causes atomization or vaporization of the liquid so that the particles may be deposited on the substrate surface. An example of such a coating process is described in U.S. Pat. Nos. 6,620,454; 6,440,491; 6,087,012; 6,001,486; and 5,725,957, which are hereby incorporated herein by reference.
An example of such a coating system or process is shown in FIG. 1. In such a coating system or process, an operator typically will place one substrate 1 or multiple substrates, such as six or so, into a coating chamber 2 and in a generally vertical orientation. After the substrates are positioned in the chamber, the high pressure air compressor 3 may be directed at the liquid coating material or solution or precursor solution 4 to atomize the particles. The high pressure air compressor may be operable to supply pressurized air at about 240 p.s.i. or thereabouts at the discharge end of the coating device. The high pressure air system generates a turbulent, random and generally uncontrolled spray or cloud of particles generally at the substrates. A low pressure air compressor 5 may then spray or guide some of the cloud of atomized coating particles toward the substrates to coat the substrate surface. The high pressure air system thus may tend to spray or blow the particles generally toward the substrates, but with a substantial amount of the particles missing the substrates and remaining in the air.
Due to the vapor or overspray or excess particles in the air after the high pressure atomization, the air in the chamber and surrounding the substrates is often circulated, such as via a large volume and high flow rate circulation and ventilation system 6, such as a circulation system or heating ventilation and air conditioning (HVAC) system operable to blow or move about 8000 cubic feet per minute (cfm) through the room and generally over the coated substrates, to remove the contaminated air from the chamber to limit or reduce unwanted particles from depositing on the substrates, which may cause irregularities in the surface coating. The removed contaminated air is exhausted from the chamber at an exhaust 7 and filtered by a filtration system 8 and burned or oxidized by an oxidation system 9 to remove the particles from the air before the air is exhausted to the atmosphere. The exhaust system, filtration system and oxidization system also are often specialized systems, in order to handle the high flow rate, such as about 8000 cfm or so, that is circulated by the HVAC system. The coated substrates are then manually removed from the chamber and uncoated substrates are manually placed in the chamber and the process is repeated.
Although such processes or systems or techniques work well for their intended purposes, there is often substantial waste of the coating material due to the high pressure air, which causes the liquid coating material to atomize or vaporize in a generally cloud-like form. The amount of waste is often in the range of about 80-90 percent or more of the material or solution that is atomized. Also, due to the difficulties in controlling the vaporized or airborne particles, the size of the airborne particles may vary, such that a non-uniform coating may occur at the substrate surface. Such known coating processes are typically manual labor intensive, and the capital costs associated with such high pressure atomizing systems and high flow air circulation systems and filtration and oxidation systems are often significant, such that the coating system may be costly to implement and to operate.
Therefore, there is a need in the art for a coating process or system that overcomes the shortcomings of the prior art.